#!/usr/bin/env python
# -*- coding: utf-8 -*-
# @Software: PyCharm
# @Version : Python-
# @Author  : Shengji He
# @Email   : hsjbit@163.com
# @File    : RedundantConnection2.py
# @Time    : 2020/9/17 9:48
# @Description:
from typing import List


class UnionFind:
    def __init__(self, n):
        self.ancestor = list(range(n))

    def union(self, index1: int, index2: int):
        self.ancestor[self.find(index1)] = self.find(index2)

    def find(self, index: int) -> int:
        if self.ancestor[index] != index:
            self.ancestor[index] = self.find(self.ancestor[index])
        return self.ancestor[index]


class Solution:
    def findRedundantDirectedConnection(self, edges: List[List[int]]) -> List[int]:
        """
        In this problem, a rooted tree is a directed graph such that, there is exactly one node (the root) for
        which all other nodes are descendants of this node, plus every node has exactly one parent, except for
        the root node which has no parents.

        The given input is a directed graph that started as a rooted tree with N nodes (with distinct
        values 1, 2, ..., N), with one additional directed edge added. The added edge has two different vertices
        chosen from 1 to N, and was not an edge that already existed.

        The resulting graph is given as a 2D-array of edges. Each element of edges is a pair [u, v] that represents
        a directed edge connecting nodes u and v, where u is a parent of child v.

        Return an edge that can be removed so that the resulting graph is a rooted tree of N nodes. If there are
        multiple answers, return the answer that occurs last in the given 2D-array.

        Example 1:
            Input: [[1,2], [1,3], [2,3]]
            Output: [2,3]
            Explanation: The given directed graph will be like this:
                  1
                 / \
                v   v
                2-->3
        Example 2:
            Input: [[1,2], [2,3], [3,4], [4,1], [1,5]]
            Output: [4,1]
            Explanation: The given directed graph will be like this:
                5 <- 1 -> 2
                     ^    |
                     |    v
                     4 <- 3
        Note:
            - The size of the input 2D-array will be between 3 and 1000.
            - Every integer represented in the 2D-array will be between 1 and N, where N is the size of the input array.

        :param edges:
        :return:
        """
        nodesCount = len(edges)
        uf = UnionFind(nodesCount + 1)
        parent = list(range(nodesCount + 1))
        conflict = -1
        cycle = -1
        for i, (node1, node2) in enumerate(edges):
            if parent[node2] != node2:
                conflict = i
            else:
                parent[node2] = node1
                if uf.find(node1) == uf.find(node2):
                    cycle = i
                else:
                    uf.union(node1, node2)
        if conflict < 0:
            return [edges[cycle][0], edges[cycle][1]]
        else:
            conflictEdge = edges[conflict]
            if cycle >= 0:
                return [parent[conflictEdge[1]], conflictEdge[1]]
            else:
                return [conflictEdge[0], conflictEdge[1]]


if __name__ == '__main__':
    S = Solution()
    edges = [[1, 2], [1, 3], [2, 3]]
    print(S.findRedundantDirectedConnection(edges))
    print('done')
